The invention relates to a soldering machine comprising: a vessel opened at the top for filling with solder; at least two solder towers placed in the vessel, each adapted for delivering a flow of solder; from an upper portion of the tower and a transporting member for carrying along the objects for soldering above the solder towers.
Such soldering devices are generally known.
The problem often arises with such soldering devices that the solder flows falling back into the vessel cause splashes of solder which can spatter so high that they make contact with the underside of the objects for soldering such as the printed circuit boards for soldering.
This problem occurs particularly, although not exclusively, in soldering machines, wherein the soldering-process takes place inside an atmosphere of inert gas. These splashed solder droplets will make contact with the underside of the circuit board where they form solder globules. These globules adhere weakly to the other solder which is already on the circuit board so that there is a danger of them coming loose at a later time and short-circuiting another circuit portion. Although this problem occurs in the case of normal soldering machines placed in a normal atmosphere, the problem arises to a greater extent in soldering machines operating in an atmosphere substantially excluding oxygen. The low-oxygen atmosphere probably results in an increase of the surface tension, whereby the formation of droplets and globules of solder is stimulated.
The object of the present invention is to avoid the above stated problems.
This object is achieved in that the solder towers are adapted for generating solder jets directed toward each other, wherein the solder jets intersect before they make contact with the solder level prevailing in the vessel. As a result of these steps the, splashes caused by the fall of the combined solder jet on the solder level are shielded from the circuit board transported thereabove so that it is no longer possible for the solder splashes to contact the surface of the objects for soldering.
Similar problems occur when the object for soldering leaves the final solder jet. In this situation, certainly when the soldering process takes place in a nitrogen atmosphere, the solder also has the tendency to form globules on the object for soldering at the position where the solder wave leaves the object for soldering.
According to a preferred embodiment of the present invention the rear tower in the direction of movement is adapted for generating a jet of solder comprising a movement component counter to the movement of the objects for soldering.
As a result of this step any globules that may have formed are washed away by the solder jet so that the problems of such solder globules are prevented.